Participants in this open label study will be randomly assigned to receive CBT for 6 to 14 weeks either through the stepped-care approach or immediately upon study entry. Participants will report to the study site for treatments and assessments on a regular basis, ranging from every 2 weeks to twice a week, depending on the stage of the study and the assigned treatment group. Stepped-care CBT will begin with self-administered EX/RP combined with counseling to address medication issues, life stress, and motivational enhancement. If ineffective, this treatment will be followed by therapist-administered EX/RP. OCD symptoms will be assessed at Week 6. Participants who have responded to treatment after 6 weeks will not receive further treatment. All others will continue for an additional 8 weeks. These participants' OCD symptoms will be assessed again at Week 14. Participants assigned to the stepped-care approach whose OCD symptoms improved initially, but relapsed without further treatment by the Week 14 evaluation will receive full-scale CBT. Outcomes will be assessed again at 1- and 3-month follow-up visits.